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1 /*
2  * Copyright © 2012  Google, Inc.
3  *
4  *  This is part of HarfBuzz, a text shaping library.
5  *
6  * Permission is hereby granted, without written agreement and without
7  * license or royalty fees, to use, copy, modify, and distribute this
8  * software and its documentation for any purpose, provided that the
9  * above copyright notice and the following two paragraphs appear in
10  * all copies of this software.
11  *
12  * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
13  * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
14  * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
15  * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
16  * DAMAGE.
17  *
18  * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
19  * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
20  * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
21  * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
22  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
23  *
24  * Google Author(s): Behdad Esfahbod
25  */
26 
27 #ifndef HB_OT_SHAPE_COMPLEX_ARABIC_FALLBACK_HH
28 #define HB_OT_SHAPE_COMPLEX_ARABIC_FALLBACK_HH
29 
30 #include "hb-private.hh"
31 
32 #include "hb-ot-shape-private.hh"
33 #include "hb-ot-layout-gsub-table.hh"
34 
35 
36 /* Features ordered the same as the entries in shaping_table rows,
37  * followed by rlig.  Don't change. */
38 static const hb_tag_t arabic_fallback_features[] =
39 {
40   HB_TAG('i','n','i','t'),
41   HB_TAG('m','e','d','i'),
42   HB_TAG('f','i','n','a'),
43   HB_TAG('i','s','o','l'),
44   HB_TAG('r','l','i','g'),
45 };
46 
47 static OT::SubstLookup *
arabic_fallback_synthesize_lookup_single(const hb_ot_shape_plan_t * plan HB_UNUSED,hb_font_t * font,unsigned int feature_index)48 arabic_fallback_synthesize_lookup_single (const hb_ot_shape_plan_t *plan HB_UNUSED,
49 					  hb_font_t *font,
50 					  unsigned int feature_index)
51 {
52   OT::GlyphID glyphs[SHAPING_TABLE_LAST - SHAPING_TABLE_FIRST + 1];
53   OT::GlyphID substitutes[SHAPING_TABLE_LAST - SHAPING_TABLE_FIRST + 1];
54   unsigned int num_glyphs = 0;
55 
56   /* Populate arrays */
57   for (hb_codepoint_t u = SHAPING_TABLE_FIRST; u < SHAPING_TABLE_LAST + 1; u++)
58   {
59     hb_codepoint_t s = shaping_table[u - SHAPING_TABLE_FIRST][feature_index];
60     hb_codepoint_t u_glyph, s_glyph;
61 
62     if (!s ||
63 	!hb_font_get_glyph (font, u, 0, &u_glyph) ||
64 	!hb_font_get_glyph (font, s, 0, &s_glyph) ||
65 	u_glyph == s_glyph ||
66 	u_glyph > 0xFFFFu || s_glyph > 0xFFFFu)
67       continue;
68 
69     glyphs[num_glyphs].set (u_glyph);
70     substitutes[num_glyphs].set (s_glyph);
71 
72     num_glyphs++;
73   }
74 
75   if (!num_glyphs)
76     return NULL;
77 
78   /* Bubble-sort or something equally good!
79    * May not be good-enough for presidential candidate interviews, but good-enough for us... */
80   hb_stable_sort (&glyphs[0], num_glyphs, OT::GlyphID::cmp, &substitutes[0]);
81 
82   OT::Supplier<OT::GlyphID> glyphs_supplier      (glyphs, num_glyphs);
83   OT::Supplier<OT::GlyphID> substitutes_supplier (substitutes, num_glyphs);
84 
85   /* Each glyph takes four bytes max, and there's some overhead. */
86   char buf[(SHAPING_TABLE_LAST - SHAPING_TABLE_FIRST + 1) * 4 + 128];
87   OT::hb_serialize_context_t c (buf, sizeof (buf));
88   OT::SubstLookup *lookup = c.start_serialize<OT::SubstLookup> ();
89   bool ret = lookup->serialize_single (&c,
90 				       OT::LookupFlag::IgnoreMarks,
91 				       glyphs_supplier,
92 				       substitutes_supplier,
93 				       num_glyphs);
94   c.end_serialize ();
95   /* TODO sanitize the results? */
96 
97   return ret ? c.copy<OT::SubstLookup> () : NULL;
98 }
99 
100 static OT::SubstLookup *
arabic_fallback_synthesize_lookup_ligature(const hb_ot_shape_plan_t * plan HB_UNUSED,hb_font_t * font)101 arabic_fallback_synthesize_lookup_ligature (const hb_ot_shape_plan_t *plan HB_UNUSED,
102 					    hb_font_t *font)
103 {
104   OT::GlyphID first_glyphs[ARRAY_LENGTH_CONST (ligature_table)];
105   unsigned int first_glyphs_indirection[ARRAY_LENGTH_CONST (ligature_table)];
106   unsigned int ligature_per_first_glyph_count_list[ARRAY_LENGTH_CONST (first_glyphs)];
107   unsigned int num_first_glyphs = 0;
108 
109   /* We know that all our ligatures are 2-component */
110   OT::GlyphID ligature_list[ARRAY_LENGTH_CONST (first_glyphs) * ARRAY_LENGTH_CONST(ligature_table[0].ligatures)];
111   unsigned int component_count_list[ARRAY_LENGTH_CONST (ligature_list)];
112   OT::GlyphID component_list[ARRAY_LENGTH_CONST (ligature_list) * 1/* One extra component per ligature */];
113   unsigned int num_ligatures = 0;
114 
115   /* Populate arrays */
116 
117   /* Sort out the first-glyphs */
118   for (unsigned int first_glyph_idx = 0; first_glyph_idx < ARRAY_LENGTH (first_glyphs); first_glyph_idx++)
119   {
120     hb_codepoint_t first_u = ligature_table[first_glyph_idx].first;
121     hb_codepoint_t first_glyph;
122     if (!hb_font_get_glyph (font, first_u, 0, &first_glyph))
123       continue;
124     first_glyphs[num_first_glyphs].set (first_glyph);
125     ligature_per_first_glyph_count_list[num_first_glyphs] = 0;
126     first_glyphs_indirection[num_first_glyphs] = first_glyph_idx;
127     num_first_glyphs++;
128   }
129   hb_stable_sort (&first_glyphs[0], num_first_glyphs, OT::GlyphID::cmp, &first_glyphs_indirection[0]);
130 
131   /* Now that the first-glyphs are sorted, walk again, populate ligatures. */
132   for (unsigned int i = 0; i < num_first_glyphs; i++)
133   {
134     unsigned int first_glyph_idx = first_glyphs_indirection[i];
135 
136     for (unsigned int second_glyph_idx = 0; second_glyph_idx < ARRAY_LENGTH (ligature_table[0].ligatures); second_glyph_idx++)
137     {
138       hb_codepoint_t second_u   = ligature_table[first_glyph_idx].ligatures[second_glyph_idx].second;
139       hb_codepoint_t ligature_u = ligature_table[first_glyph_idx].ligatures[second_glyph_idx].ligature;
140       hb_codepoint_t second_glyph, ligature_glyph;
141       if (!second_u ||
142 	  !hb_font_get_glyph (font, second_u,   0, &second_glyph) ||
143 	  !hb_font_get_glyph (font, ligature_u, 0, &ligature_glyph))
144 	continue;
145 
146       ligature_per_first_glyph_count_list[i]++;
147 
148       ligature_list[num_ligatures].set (ligature_glyph);
149       component_count_list[num_ligatures] = 2;
150       component_list[num_ligatures].set (second_glyph);
151       num_ligatures++;
152     }
153   }
154 
155   if (!num_ligatures)
156     return NULL;
157 
158   OT::Supplier<OT::GlyphID>   first_glyphs_supplier                      (first_glyphs, num_first_glyphs);
159   OT::Supplier<unsigned int > ligature_per_first_glyph_count_supplier    (ligature_per_first_glyph_count_list, num_first_glyphs);
160   OT::Supplier<OT::GlyphID>   ligatures_supplier                         (ligature_list, num_ligatures);
161   OT::Supplier<unsigned int > component_count_supplier                   (component_count_list, num_ligatures);
162   OT::Supplier<OT::GlyphID>   component_supplier                         (component_list, num_ligatures);
163 
164   /* 16 bytes per ligature ought to be enough... */
165   char buf[ARRAY_LENGTH_CONST (ligature_list) * 16 + 128];
166   OT::hb_serialize_context_t c (buf, sizeof (buf));
167   OT::SubstLookup *lookup = c.start_serialize<OT::SubstLookup> ();
168   bool ret = lookup->serialize_ligature (&c,
169 					 OT::LookupFlag::IgnoreMarks,
170 					 first_glyphs_supplier,
171 					 ligature_per_first_glyph_count_supplier,
172 					 num_first_glyphs,
173 					 ligatures_supplier,
174 					 component_count_supplier,
175 					 component_supplier);
176 
177   c.end_serialize ();
178   /* TODO sanitize the results? */
179 
180   return ret ? c.copy<OT::SubstLookup> () : NULL;
181 }
182 
183 static OT::SubstLookup *
arabic_fallback_synthesize_lookup(const hb_ot_shape_plan_t * plan,hb_font_t * font,unsigned int feature_index)184 arabic_fallback_synthesize_lookup (const hb_ot_shape_plan_t *plan,
185 				   hb_font_t *font,
186 				   unsigned int feature_index)
187 {
188   if (feature_index < 4)
189     return arabic_fallback_synthesize_lookup_single (plan, font, feature_index);
190   else
191     return arabic_fallback_synthesize_lookup_ligature (plan, font);
192 }
193 
194 #define ARABIC_FALLBACK_MAX_LOOKUPS 5
195 
196 struct arabic_fallback_plan_t
197 {
198   ASSERT_POD ();
199 
200   unsigned int num_lookups;
201   bool free_lookups;
202 
203   hb_mask_t mask_array[ARABIC_FALLBACK_MAX_LOOKUPS];
204   OT::SubstLookup *lookup_array[ARABIC_FALLBACK_MAX_LOOKUPS];
205   hb_ot_layout_lookup_accelerator_t accel_array[ARABIC_FALLBACK_MAX_LOOKUPS];
206 };
207 
208 static const arabic_fallback_plan_t arabic_fallback_plan_nil = {};
209 
210 #if (defined(_WIN32) || defined(__CYGWIN__)) && !defined(HB_NO_WIN1256)
211 #define HB_WITH_WIN1256
212 #endif
213 
214 #ifdef HB_WITH_WIN1256
215 #include "hb-ot-shape-complex-arabic-win1256.hh"
216 #endif
217 
218 struct ManifestLookup {
219   OT::Tag tag;
220   OT::OffsetTo<OT::SubstLookup> lookupOffset;
221 };
222 typedef OT::ArrayOf<ManifestLookup> Manifest;
223 
224 static bool
arabic_fallback_plan_init_win1256(arabic_fallback_plan_t * fallback_plan,const hb_ot_shape_plan_t * plan,hb_font_t * font)225 arabic_fallback_plan_init_win1256 (arabic_fallback_plan_t *fallback_plan,
226 				   const hb_ot_shape_plan_t *plan,
227 				   hb_font_t *font)
228 {
229 #ifdef HB_WITH_WIN1256
230   /* Does this font look like it's Windows-1256-encoded? */
231   hb_codepoint_t g;
232   if (!(hb_font_get_glyph (font, 0x0627u, 0, &g) && g == 199 /* ALEF */ &&
233 	hb_font_get_glyph (font, 0x0644u, 0, &g) && g == 225 /* LAM */ &&
234 	hb_font_get_glyph (font, 0x0649u, 0, &g) && g == 236 /* ALEF MAKSURA */ &&
235 	hb_font_get_glyph (font, 0x064Au, 0, &g) && g == 237 /* YEH */ &&
236 	hb_font_get_glyph (font, 0x0652u, 0, &g) && g == 250 /* SUKUN */))
237     return false;
238 
239   const Manifest &manifest = reinterpret_cast<const Manifest&> (arabic_win1256_gsub_lookups.manifest);
240   ASSERT_STATIC (sizeof (arabic_win1256_gsub_lookups.manifestData) / sizeof (ManifestLookup)
241 		 <= ARABIC_FALLBACK_MAX_LOOKUPS);
242   /* TODO sanitize the table? */
243 
244   unsigned j = 0;
245   unsigned int count = manifest.len;
246   for (unsigned int i = 0; i < count; i++)
247   {
248     fallback_plan->mask_array[j] = plan->map.get_1_mask (manifest[i].tag);
249     if (fallback_plan->mask_array[j])
250     {
251       fallback_plan->lookup_array[j] = const_cast<OT::SubstLookup*> (&(&manifest+manifest[i].lookupOffset));
252       if (fallback_plan->lookup_array[j])
253       {
254 	fallback_plan->accel_array[j].init (*fallback_plan->lookup_array[j]);
255 	j++;
256       }
257     }
258   }
259 
260   fallback_plan->num_lookups = j;
261   fallback_plan->free_lookups = false;
262 
263   return j > 0;
264 #else
265   return false;
266 #endif
267 }
268 
269 static bool
arabic_fallback_plan_init_unicode(arabic_fallback_plan_t * fallback_plan,const hb_ot_shape_plan_t * plan,hb_font_t * font)270 arabic_fallback_plan_init_unicode (arabic_fallback_plan_t *fallback_plan,
271 				   const hb_ot_shape_plan_t *plan,
272 				   hb_font_t *font)
273 {
274   ASSERT_STATIC (ARRAY_LENGTH_CONST(arabic_fallback_features) <= ARABIC_FALLBACK_MAX_LOOKUPS);
275   unsigned int j = 0;
276   for (unsigned int i = 0; i < ARRAY_LENGTH(arabic_fallback_features) ; i++)
277   {
278     fallback_plan->mask_array[j] = plan->map.get_1_mask (arabic_fallback_features[i]);
279     if (fallback_plan->mask_array[j])
280     {
281       fallback_plan->lookup_array[j] = arabic_fallback_synthesize_lookup (plan, font, i);
282       if (fallback_plan->lookup_array[j])
283       {
284 	fallback_plan->accel_array[j].init (*fallback_plan->lookup_array[j]);
285 	j++;
286       }
287     }
288   }
289 
290   fallback_plan->num_lookups = j;
291   fallback_plan->free_lookups = true;
292 
293   return j > 0;
294 }
295 
296 static arabic_fallback_plan_t *
arabic_fallback_plan_create(const hb_ot_shape_plan_t * plan,hb_font_t * font)297 arabic_fallback_plan_create (const hb_ot_shape_plan_t *plan,
298 			     hb_font_t *font)
299 {
300   arabic_fallback_plan_t *fallback_plan = (arabic_fallback_plan_t *) calloc (1, sizeof (arabic_fallback_plan_t));
301   if (unlikely (!fallback_plan))
302     return const_cast<arabic_fallback_plan_t *> (&arabic_fallback_plan_nil);
303 
304   fallback_plan->num_lookups = 0;
305   fallback_plan->free_lookups = false;
306 
307   /* Try synthesizing GSUB table using Unicode Arabic Presentation Forms,
308    * in case the font has cmap entries for the presentation-forms characters. */
309   if (arabic_fallback_plan_init_unicode (fallback_plan, plan, font))
310     return fallback_plan;
311 
312   /* See if this looks like a Windows-1256-encoded font.  If it does, use a
313    * hand-coded GSUB table. */
314   if (arabic_fallback_plan_init_win1256 (fallback_plan, plan, font))
315     return fallback_plan;
316 
317   free (fallback_plan);
318   return const_cast<arabic_fallback_plan_t *> (&arabic_fallback_plan_nil);
319 }
320 
321 static void
arabic_fallback_plan_destroy(arabic_fallback_plan_t * fallback_plan)322 arabic_fallback_plan_destroy (arabic_fallback_plan_t *fallback_plan)
323 {
324   if (!fallback_plan || fallback_plan == &arabic_fallback_plan_nil)
325     return;
326 
327   for (unsigned int i = 0; i < fallback_plan->num_lookups; i++)
328     if (fallback_plan->lookup_array[i])
329     {
330       fallback_plan->accel_array[i].fini ();
331       if (fallback_plan->free_lookups)
332 	free (fallback_plan->lookup_array[i]);
333     }
334 
335   free (fallback_plan);
336 }
337 
338 static void
arabic_fallback_plan_shape(arabic_fallback_plan_t * fallback_plan,hb_font_t * font,hb_buffer_t * buffer)339 arabic_fallback_plan_shape (arabic_fallback_plan_t *fallback_plan,
340 			    hb_font_t *font,
341 			    hb_buffer_t *buffer)
342 {
343   OT::hb_apply_context_t c (0, font, buffer);
344   for (unsigned int i = 0; i < fallback_plan->num_lookups; i++)
345     if (fallback_plan->lookup_array[i]) {
346       c.set_lookup_mask (fallback_plan->mask_array[i]);
347       hb_ot_layout_substitute_lookup (&c,
348 				      *fallback_plan->lookup_array[i],
349 				      fallback_plan->accel_array[i]);
350     }
351 }
352 
353 
354 #endif /* HB_OT_SHAPE_COMPLEX_ARABIC_FALLBACK_HH */
355